RF3145 Просмотр технического описания (PDF) - RF Micro Devices
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RF3145 Datasheet PDF : 18 Pages
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RF3145
P----P---A----+-----P----L---O---S---S
-P---I--N-
ηEFF
=
1----0------------1---0-------------–-----1---0----1--0--
VBAT ⋅ IBAT ⋅ 10
(Eq. 3)
Where PPA is the output power from the PA, PLOSS the insertion loss, PIN the input power to the PA, and PDC the delivered DC
power.
The RF3145 improves the effective efficiency by minimizing the PLOSS term in the equation. A directional coupler may introduce
0.4dB to 0.5dB loss to the transit path. To demonstrate the improvement in effective efficiency consider the following exam-
ple:
Conventional PA Solution:
PPA = +33.5 dBm
PIN = +3 dBm
PLOSS = -0.4 dB
VBAT = 3.5 V
IBAT = 1.16 A
ηEFF = 50.3%
RF3145 Solution:
PPA = +33.5 dBm
PIN = +3 dBm
PLOSS = 0 dB
VBAT = 3.5 V
IBAT = 1.16 A
hEFF = 55.16%
The RF3145 solution improves effective efficiency 5percent.
Output power does not vary due to supply voltage under normal operating conditions if VRAMP is sufficiently lower than VBATT.
By regulating the collector voltage to the PA, the voltage sensitivity is essentially eliminated. This covers most cases where the
PA will be operated. However, as the battery discharges and approaches its lower power range, the maximum output power
from the PA will also drop slightly. In this case it is important to also decrease VRAMP to prevent the power control from inducing
switching transients. These transients occur as a result of the control loop slowing down and not regulating power in accor-
dance with VRAMP.
The switching transients due to low battery conditions are regulated by incorporating the following relationship limiting the
maximum VRAMP voltage (Equation 4). Although no compensation is required for typical battery conditions, the battery compen-
sation required for extreme conditions is covered by the relationship in Equation 4. This should be added to the terminal soft-
ware.
VRAMP
≤
3--
8
⋅
VBATT
+
0.18
(Eq. 4)
NOTE: Output power is limited by battery voltage. The relationship in Equation 4 does not limit output power. Equation 4 limits
the VRAMP voltage to correspond with the battery voltage.
Due to reactive output matches, there are output power variations across frequency. There are a number of components that
can make the effects greater or less.
Rev A4 DS050919
7628 Thorndike Road, Greensboro, NC 27409-9421 · For sales or technical
support, contact RFMD at (+1) 336-678-5570 or sales-support@rfmd.com.
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